1. Field of the Invention
The present invention relates to multiphase DC/DC converters, and more particularly to removing a phase in a multiphase DC/DC converter while minimizing disturbance of the output voltage.
2. Description of the Related Art
Multiphase DC/DC converters distribute current to a load among multiple phases or channels to provide increased output power and to improve efficiency at high load levels. Many electronic devices include a low-power or reduced power mode to conserve energy or battery power. The multiphase converter becomes less efficient at lower power levels while all phases remain active, so that it is desired to shut down one or more phases during lower power levels to improve efficiency. Control logic of the device determines or detects power requirements and asserts a low power signal or the like to initiate a low power state. For example, many microprocessors detect or otherwise determine that less power is needed and that a reduced power mode of operation is advantageous.
In response to the low power signal, conventional multiphase DC/DC converters simply turned off a phase without adjusting the remaining one or more phases that remained active. Suddenly shutting down one or more phases caused the output voltage to decrease. The feedback loop operative to maintain the output voltage level responded to the reduced output voltage and adjusted the current in the remaining active phases to increase the falling output voltage back to the target level. The loop response, however, was insufficient to prevent a significant albeit temporary dip in the output voltage. The temporary decrease in output voltage may have deleterious effects on the system, and reduces overall efficiency.
It is desired to avoid a significant decrease in the output voltage level when removing one or more phases to achieve low power mode.